Abstract: The tank volume will change when the average temperature of tank-shell is not at 20℃ in the measurement of vertical tank. Although there are many ways to calculate the change at present, the calculation deviation is evident. This paper analyzes the applicable conditions of various formulae, and points out that the deviation comparison should be done between the formulae in accordance with actual site data so as to determine the applicable scope for them. In the paper, the average tank-shell temperature formula is recommanded.